The soldiers are upon us - and resistance is futile

The Terracotta Army is the greatest work of mass-production art in history, yet each man, from archer to general, is a distinct individual. The platoon visiting Britain is small, but it's endlessly fascinating

The First Emperor: China's Terracotta Army, British Museum, London WC1, until 6 April. To book: 020 7323 8181

At the ready - forever - the archer waits with his bow, down on one knee, biceps flexed, eyes fixed upon the future. Should anything move he will shoot it for certain. He holds a pose so tense in its torsion you marvel at the perfect discipline. The archer is a past master, but also a masterpiece, of devastating stillness.

This terracotta figure has kept watch over China's First Emperor for 2,000 years and might have done so eternally, unseen beneath the earth, had it not been for the farmer who took a spade 30 years ago and starting digging the field above the underground necropolis. It still seems unbelievable that nobody, other than some 1st-century tomb-raiders, chanced upon the First Emperor's buried army before 1974. But more mysterious by far is the fact that these figures, with all their stupendous realism, are without precedent in Chinese art. They may look like the climax of some long tradition yet there was nothing like them before 210BC, and there's been nothing like them ever since.

It is the realism of something more than basic facsimile. You can see, for instance, that the archer's plaits have too often been lacquered with starch, that the centre-parting doesn't really suit him though his long, strong fingers must have been perfect for the job. But you can also see that he was powerfully handsome in a square-jawed kind of way and yet not obviously vain, unlike the light infantryman nearby who takes such pride in his silken looks.

There are 8,000 warriors in the Terracotta Army and yet no two figures are alike, and it is not just a matter of superficial detail. No scarf or moustache is exactly alike, and every pair of shoes is slightly different. But what is far more astonishing is that every warrior is his own man: that every man stands out from the next. Surely the terracotta soldiers are in some sense actual portraits?

Here is the advantage of this epochal show, the first time so many of the figures - 20 in total - have been shown together in a museum outside China. The detachment may sound disappointingly small, but what you get instead of the immense throngs standing shoulder to shoulder in their burial pits outside present-day Xian is the chance to come face to face with each man, to experience each personality: irritable, patient, bullish, reserved, the old general, the young tyro in his stylish cap. This is not the anonymous and mechanical phalanx of modern war art but the army as individual soldiers.

Were they portraits? Scholars say not, but I find this impossible to believe. Look at this little group of characters and then imagine the commission multiplied over and over again until it reaches 8,000. These faces came alive through the observations of the people who made them. Somewhere in this great mass of sculptures are the likenesses of real people, of real soldiers and quite possibly of the artists themselves: the men who gave spirit to these faces.

And here is another mystery: the Terracotta Army is the greatest work of mass-production art in history, made by more than 1,000 men including prisoners of war and convicts, or so it is said. Craftsmen who used to make drainpipes somehow adapted their technique to make soldiers' legs. Hands, limbs and torsos were assembled by a production line of sweated labour. Yet there must have been a high number of master-artists in their midst - the last hands to touch each face, to adjust a mouth into the hint of a smile, to raise an eyebrow into perceptible impatience.

In Europe no such thing occurred until the Middle Ages, and even in Ancient Greece and Egypt you don't see such painstaking expressions of individual identity except in portraits of single emperors and pharaohs, let alone ordinary soldiers by the thousand. It is true that these figures have no visionary uplift, like the animal-gods of the Nile or the Winged Victory of Samothrace. But reality is their point. They are meant to stand to attention; they are meant to do their job.

One certainty, however, is that they were never made to be viewed, still less admired as works of art. They were never meant to be seen at all, in fact, at least not on this side of the afterlife.

Sightless now, these warriors once had painted eyes and were coloured head to toe. Surrogates of the living, they were in no sense sculptures to the Emperor. His necropolis was an exact replica of life as lived above the ground, right down to the parks, the exotic birds, the bronze horse-drawn carriages and the massed ranks of soldiers.

The Emperor's tomb has never been excavated and nobody knows what might be found within that enormous area beneath the ground, although the stories of starry heavens made of pearls and rivers of running mercury must have some truth in them, for pearls and mercury have both been found near the site. But it is known that many of the artists who made the Terracotta Army were buried alive with the Emperor when he died, very suddenly, at the age of 49. Perhaps he thought they would keep on working for all eternity, just as he would rule forever. Or perhaps he made no distinction between the life-like and the living.